Photoelectromagnetic Effect Induced by Terahertz Laser Radiation in Topological Crystalline Insulators PbSnTe.

Topological crystalline insulators form a class of semiconductors for which surface electron states with the Dirac dispersion relation are formed on surfaces with a certain crystallographic orientation. PbSnTe alloys belong to the topological crystalline phase when the SnTe content exceeds 0.35, while they are in the trivial phase at < 0.

Triple-Point Fermions in Ferroelectric GeTe.

Ferroelectric α-GeTe is unveiled to exhibit an intriguing multiple nontrivial topology of the electronic band structure due to the existence of triple-point and type-II Weyl fermions, which goes well beyond the giant Rashba spin splitting controlled by external fields as previously reported. Using spin- and angle-resolved photoemission spectroscopy combined with ab initio density functional theory, the unique spin texture around the triple point caused by the crossing of one spin-degenerate and two spin-split bands along the ferroelectric crystal axis is derived. This consistently reveals spin winding numbers that are coupled with time-reversal symmetry and Lorentz invariance, which are found to be equal for both triple-point pairs in the Brillouin zone.

Topological quantum phase transition from mirror to time reversal symmetry protected topological insulator.

Topological insulators constitute a new phase of matter protected by symmetries. Time-reversal symmetry protects strong topological insulators of the Z class, which possess an odd number of metallic surface states with dispersion of a Dirac cone. Topological crystalline insulators are merely protected by individual crystal symmetries and exist for an even number of Dirac cones.

Giant Rashba Splitting in Pb Sn Te (111) Topological Crystalline Insulator Films Controlled by Bi Doping in the Bulk.

The topological properties of lead-tin chalcogenide topological crystalline insulators can be widely tuned by temperature and composition. It is shown that bulk Bi doping of epitaxial Pb Sn Te (111) films induces a giant Rashba splitting at the surface that can be tuned by the doping level. Tight binding calculations identify their origin as Fermi level pinning by trap states at the surface.

The mechanism of Bi nanowire growth from Bi/Co immiscible composite thin films.

Single crystalline Bi nanowires were grown by extrusion from Bi/Co thin films. The films were obtained by thermal evaporation in high vacuum. The average diameter, length and density of obtained nanowires were 100 nm, 30 microm and 6.